This invention relates generally to disconnect switches, and, more particularly, to fused disconnect switches.
Fuses are widely used as overcurrent protection devices to prevent costly damage to electrical circuits. Fuse terminals typically form an electrical connection between an electrical power source and an electrical component or a combination of components arranged in an electrical circuit. One or more fusible links or elements, or a fuse element assembly, is connected between the fuse terminals, so that when electrical current through the fuse exceeds a predetermined limit, the fusible elements melt and opens one or more circuits through the fuse to prevent electrical component damage.
In some applications, fuses are employed not only to provide fused electrical connections but also for connection and disconnection, or switching, purposes to complete or break an electrical connection or connections. As such, an electrical circuit is completed or broken through conductive portions of the fuse, thereby energizing or de-energizing the associated circuitry. Typically, the fuse is housed in a fuse holder having terminals that are electrically coupled to desired circuitry. When conductive portions of the fuse, such as fuse blades, terminals, or ferrules, are engaged to the fuse holder terminals, an electrical circuit is completed through the fuse, and when conductive portions of the fuse are disengaged from the fuse holder terminals, the electrical circuit through the fuse is broken. Therefore, by inserting and removing the fuse to and from the fuse holder terminals, a fused disconnect switch is realized.
Known fused disconnect switches of this type, however, are disadvantaged in certain applications. For instance, in telecommunications applications, increasing power demands of equipment loads have rendered many fused disconnect switches inadequate. In addition, limited field wiring options can frustrate the use of a common line input bus and may require auxiliary components for connection to telecommunication distribution panels. Still further, especially when a large number of disconnect switches are employed, quick and accurate identification of opened fuses is necessary so that opened fuses may be identified and replaced. Conventional fuse state identification mechanisms are not as reliable as desired for telecommunications applications. For at least the above reasons, use of fused disconnect switches have not completely met the needs of certain end applications, such as use in telecommunications systems.